[Cephalic region damage in the nemertean Lineus ruber by the orthonectid Intoshia linei]

Previous investigators believed, that the plasmodia of Intoshia linei can affect all part of nemerteans body except the cephalic lobe. Our results indicate that in strongly infected worms mature plasmodia can settle inside of the cephalic region and form the large conglomerates. Common places of plasmodia localization in hosts are not only the tegument, connective tissue, gonads, muscles of body wall and proboscis, but also the nervous tissue. We found a lot of the mature plasmodia in all four lobes of the nemerteans brain and in the lateral nerve trunks. Furthermore the plasmodia can settle in the cerebral organs, in the walls of blood lacunae and rhynchcoel. In spite of the strong invasion of the cephalic lobe we have never observed a plasmodial outgrowths in the tegument of this region. This phenomena can be explained by the assumption, that plasmodia usually intrude into the cephalic region relatively late and have no time to form outgrowths up to the moment when starts the emission of adult males and females in the rest parts of nemertean body. Moreover, single parasite cells were repeatedly found in the host tissue near the mature plasmodium. These cells had few cytoplasm and large vesicular nuclei, which were very similar in size to the nuclei of the host cells. General morphology of single cells was very similar to the generative cells of the plasmodium. At present, the function of these cells is not evident, but we believe, they appearance is concerned with the proliferation of plasmodiuma and agglomeration of the parasite in the body of Lineus ruber.